Dental composite material with adapted ratio of flexural strength to elastic modulus, and mill blanks made of said composite material

ABSTRACT

A polymerisable dental composite material comprising
     (i) 60 to 85% by weight of an inorganic filler component comprising at least one tectosilicate and optionally at least one dental glass and/or at least one amorphous metal oxide,   (ii) 10 to 40% by weight of a mixture of at least two different urethane(meth)acrylates,   (iii) 0.01 to 5% by weight of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane(meth)acrylate,   (iv) 0.01 to 10% by weight of at least one initiator, an initiator system and optionally at least one stabiliser and optionally at least one pigment, wherein the total composition of the composite material amounts to 100% by weight, and a polymerised composite material having a flexural strength of greater than or equal to 240 MPa and an elastic modulus of 16 to 20 GPa for the production of indirect dentures.

This application is a 371 of PCT/EP2018/076596, filed Oct. 1, 2018, which claims foreign priority benefit under 35 U.S.C. § 119 of German Patent Application No. 10 2017 123 012.2, filed Oct. 4, 2017, the disclosures of which are incorporated herein by reference.

The invention relates to a polymerisable dental composite material, comprising (i) 60 to 85% by weight of at least one inorganic filler component comprising at least one tectosilicate, in particular of an average particle size d₅₀ of 0.7 μm to 3.0 μm, as well as optionally at least one dental glass and/or at least one amorphous metal oxide, (ii) 10 to 40% by weight of a mixture of at least two different urethane(meth)acrylates, (iii) 0.01 to 5% by weight of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane(meth)acrylate, and (iv) 0.01 to 10% by weight of at least one initiator, an initiator system as well as optionally stabilisers and optionally pigments, wherein the total composition of the composite material amounts to 100% by weight, as well as a polymerised composite material having a flexural strength of greater than or equal to 240 MPa and an elastic modulus of 16 to 20 GPa (dry storage).

Many dental composites universally usable for a direct adhesive restoration as well as for the extraoral fabrication of indirect dentures are known. From the material class of dental composites, only inorganic-organic hybrid materials with larger amounts of inorganic filling materials such as e.g. dental glass and/or mineral nano agglomerates are suitable. Micro filler composites with pre-polymer fillers introduced in the 1980s are not suitable for use in the posterior region (classes I and II) due to the limited wear resistance (abrasion resistance).

A high filler content is advantageous in order to achieve very good mechanical properties of the cured composite and to reduce the polymerization shrinkage that occurs during curing at the same time. These properties are also decisive for the long-term success of the denture material.

The excellent material properties of dental composites with polyalicyclic structural elements for direct adhesive restoration, especially the low shrinkage force and high flexural strength, are well known.

It was the object of the invention to provide a dental composite material being suitable for the production of larger blocks of material, in particular of geometric moulded bodies such as milling blocks. In addition, the object was to provide a dental composite material having a homogeneous, monochrome colouring before and after polymerisation. In this context, the homogeneous, monochrome colouring should also be feasible with larger blocks of material. Furthermore, polychrome, i.e. multi-coloured blocks of material with a defined colouring should be producible. Moreover, a dental composite material should be provided that is easily flowable in the non-polymerised state and yet has excellent mechanical properties in the polymerised state and has low shrinkage during polymerisation, even when producing larger blocks of material. Furthermore, the composite material should not develop cracks or pores during curing, even with large-volume blocks of material.

Starting from state-of-the-art composites based on urethane derivatives, the filler system, the monomer mixture as well as the pigment system had to be modified. The wide particle size distribution, advantageous for high packing density and excellent mechanical properties, could not be maintained. According to the invention, a filler system was developed having high flexural strength on the one hand and at the same time a high elastic modulus but being in the range of the elastic modulus of the hard tooth tissue.

In addition, the ratio of flexural strength and elastic modulus could be further improved using a narrow particle size distribution. The average value of the particle size distribution was set to a range of 0.7 to 3.0 μm, in particular of 1.5 to 2.5 μm (micrometers), in particular to d₅₀ of 2.0 μm with plus/minus 0.25 μm. The particle size distribution was then adjusted to a range of 0.7 to 1 m. The lower packing density and reduced filler surface allow for better flowability (lower structural viscosity).

Voluminous moulded parts for the production of larger blocks of material cannot be photo-polymerised due to the limited penetration depth of the light into the composite material. For this reason, an initiator system is to be provided and to be developed.

When choosing the initiator system, care must be taken that, on the one hand, no stresses are built up in the large blocks of material due to the reaction kinetics, for example of a peroxide, in order to avoid cracking in the interior of the blocks, since the thermal conductivity of the materials is low.

Moulding for the production of the blocks of material is carried out by inserting the polymerisable dental composite material into a casting mould, hereinafter only referred to as mould, under pressure. The applied pressure is preferably between 500 and 300 MPa or [N/mm2]. Polymerization is performed at elevated temperature, preferably being in the range of about 90 to 150° C. The polymerization is carried out at a pressure of about 90 to 300 MPa or [N/mm2]. It is polymerised in a closed casting mould to minimise, preferably avoid, the formation of air bubbles. Preferably, it is polymerised under a pressure of 120 to 320 MPa, preferably to less than or equal to 300 MPa, at a temperature of 100 to 180° C., preferably about 140° C., for at least 10 minutes to 10 hours. The blocks of material preferably have a dimension of at least 1 cm in all special directions and are present as geometric moulded bodies.

Surprisingly, it has been found that composites based on a urethane monomer having an alicyclic structural element, such as tetrahydrodicyclopentadiene, are extremely well suited for the production of indirect dentures, since surprisingly high flexural strengths may be achieved by thermally initiated polymerization. The high level of polymer strength compared to the already described photopolymerization in the case of light-curing dental composites was surprising and not to be expected with these significantly increased values. At the same time, the low-shrinkage crosslinking of the relatively large amount of composite in one process step is advantageous in order to avoid stress cracks in the block/blank. High crosslinking densities being desirable for material strength can often result in unusability of the polymerised molded parts due to the high shrinkage stresses.

A subject matter of the invention is a polymerisable dental composite material, in particular a thermally polymerisable composite material, comprising

(i) 60 to 85% by weight of at least one inorganic filler component comprising at least one tectosilicate, particularly preferably at least one feldspar or mixtures thereof, in particular of an average particle size d₅₀ of 0.7 to 3.0 μm, preferably with d₅₀ of 1.5 to 2.5 μm, as well as optionally at least one dental glass and/or at least one amorphous metal oxide,

(ii) 10 to 40% by weight of a mixture of at least two different urethane(meth)acrylates, preferably of a mixture of at least three different urethane(meth)acrylates, in particular of di- to decafunctional urethane(meth)acrylates,

(iii) 0.01 to 5% by weight of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane(meth)acrylate,

(iv) 0.01 to 10% by weight of at least one initiator, of an initiator system as well as optionally of at least one stabiliser and optionally of at least one pigment, wherein in particular the at least one pigment comprises both fluorescence pigments and colour pigments, wherein the total composition of the composite material amounts to 100% by weight.

Furthermore, a subject matter of the invention is a polymerisable dental composite material, in particular a thermally polymerisable composite material, or polymerised composite material comprising

(i) 60 to 85% by weight at least one inorganic filler component,

wherein 60 to 80% by weight, based in the total composition of the composite material, correspond to at least one tectosilicate, preferably at least one anhydrous tectosilicate, i.e. tectosilicate without zeolitic H₂O, particularly preferably at least one feldspar, in particular alkali feldspar and/or lime-soda feldspar or mixture thereof, in particular of an average particle size d₅₀ of 0.7 to 3.0 μm, preferably with d₅₀ of 1.5 to 2.5 μm, as well as optionally 0 to 10% by weight, preferably 2 to 8% by weight at least one amorphous metal oxide and/or optionally 0 to 10% by weight, in particular 1 to 8% by weight at least one dental glass, based on the total composition of the composite material. The tectosilicates (without zeolitic H₂O) do not comprise the family of zeolites (with zeolitic H₂O).

Particularly preferably (i) 60 to 85% by weight are at least one inorganic filler component comprising 60 to 80% by weight, based on the total composition of the composite material, at least one tectosilicate, preferably at least one tectosilicate that do not correspond to a water-containing tectosilicate, particularly preferably at least one feldspar or a mixture thereof, as well as optionally 0.5 to 10% by weight, preferably 2 to 8% by weight at least one amorphous metal oxide, based on the total composition of the composite material.

The composite material preferably comprises 0.1 to 2% by weight at least one hexafunctional urethane(meth)acrylate or dendritic urethane methacrylate, preferably in a mixture of urethane(meth)acrylates.

In one embodiment variant, it is preferred for the thermally polymerisable composite material to be additionally photochemically polymerisable. A thermally polymerisable composite material is presently understood to mean a composite material that may be polymerised at greater than or equal to 60 to 150° C., preferably at greater than or equal to 70 to 150° C., particularly preferably from 90 to 150° C. In this context, according to the invention it is further preferred for the volume shrinkage to be less than or equal to 1.5%.

By polymerising the composite material according to the invention, a polymerised composite material having a flexural strength of greater than or equal to 240 MPa, in particular greater than or equal to 250 MPa, and an elastic modulus of 16 to 23 GPa, in particular 18 GPa to 12 GPa (dry storage), as well as preferably having a flexural strength of greater than or equal to 240 MPa and an elastic modulus of greater than or equal to 15 GPa after storage in deionised water for 7 days at 37° C. followed by thermocycling, is obtainable. The polymerised composite material is preferably present as block of material, in particular in the form of a milling blank having a dimension of at least 1 cm in all spatial directions

A polymerised composite material having a flexural strength of greater than or equal to 240 MPa to optionally 330 MPa, in particular 280 to 330 MPa (7 days, 23±2° C., dry storage) and an elastic modulus greater than or equal to 16 to 21 GPa, in particular 18 to 21 GPa (7 days, 23±2° C., dry storage) according to EN ISO 6872:2008 is obtainable from the thermally polymerisable composite material according to the invention.

Furthermore, a composite material having a flexural strength of greater than or equal to 260 MPa to 330 MPa, in particular 270 to 330 MPa (7 days of storage in H₂O deionised at 37° C.) and an elastic modulus greater than or equal to 16 to 22 GPa, in particular 18 to 22 GPa (7 days of storage in H₂O deionised at 37° C.) according to EN ISO 6872:2008 is obtainable.

Particularly preferably, a polymerised composite material having a flexural strength of greater than or equal to 240 MPa to 300 MPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds)) and an elastic modulus of greater than or equal to 15 to 22 GPa, in particular 16 to 20 GPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds)) according to EN ISO 6872:2008 from the thermally polymerisable composite material according to the invention.

The following tectosilicates are preferably considered: feldspar as well as mixtures of feldspars, in particular alkali feldspar and/or lime-soda feldspar, wherein a mixture of feldspars having a particle size of 2.0+/−0.15 μm is particularly preferred. The mixture of feldspars in the filler component preferably has a refractive index of about 1.53. In addition, it is preferred for the feldspar to be silanised, preferably with methylacrylsilanes.

Likewise preferably, the tectosilicate, in particular a feldspar, may have an average particle size d₅₀ of 0.7 to 3.0 μm, in particular i) with d₅₀ of 1.3 to 2.5 μm, in particular d₅₀ of 2.0 μm optionally with plus/minus 0.25 μm, ii) with d₅₀ of 1.5 μm optionally with plus/minus 0.25 μm, and/or iii) d₅₀ of 0.85 μm optionally with plus/minus 0.15 μm.

A feldspar the intrinsic colour of which is modified is particularly preferred. Thus, usual feldspar has an intrinsic colour of (x: 91/92, Y: 96/97, Z: 103) according to DIN 5033 for particle sizes of 0.3 to 2 micrometers. The iron content of a naturally occurring feldspar without treatment amounts to, for example about 82 ppm by weight. Therefore, the intrinsic colour of such feldspar is yellower or has a red cast. In addition, the contents of arsenic can amount to circa 0.4 ppm by weight, beryllium circa 0.6 ppm by weight, manganese circa 3.6 ppm by weight, molybdenum circa 0.5 ppm by weight, antimony circa 2.3 ppm by weight and zinc circa 124 ppm by weight.

A particularly preferably used feldspar has been treated with an organic or inorganic acid, in particular a strong acid, to reduce the content of at least one transition metal, in particular of at least one heavy metal, iron, manganese, molybdenum, antimony and/or arsenic. Thus, a particularly preferred feldspar may preferably have been treated, for example, with citric acid, sulfuric acid, hydrochloric acid, nitric acid or aqua regia. The respective iron content, manganese content and/or molybdenum content in the feldspar may be reduced each to below 50% by weight of the respective initial content. Consequently, a subject matter of the invention is polymerisable dental composite material, comprising 60 to 85% by weight of an inorganic filler component comprising at least one feldspar or a mixture comprising feldspar, in particular a feldspar mixture, which has been treated with an organic or inorganic acid or a mixture of inorganic acids selected from citric acid, sulfuric acid, hydrochloric acid, nitric acid or aqua regia, preferably has superficially been treated with an organic acid or inorganic acid or a mixture thereof, in particular to reduce the content of transition metals, preferably iron. Preferred acids are sulfuric acid, hydrochloric acid, nitric acid or aqua regia.

In addition a feldspar may preferably be used the iron content of which is less than or equal to 60 ppm by weight, preferably less than 50 ppm by weight. The colour of a feldspar accordingly modified is whiter or brighter and more transparent. Preferably, a feldspar is used the content of which of the respective transition metal below independently selected from arsenic, beryllium, manganese, molybdenum is less than or equal to 0.3 ppm by weight. The antimony content may set to less than or equal to 1.5 ppm by weight, preferably less than or equal to 1.2 ppm by weight. The zinc content may set to less than or equal to 3 ppm by weight, preferably less than or equal to 2.5 ppm by weight. Particularly preferably, the content, each independently, of arsenic is less than or equal to 0.1 ppm by weight, beryllium less than or equal to 0.3 ppm by weight, manganese less than or equal to 0.5 ppm by weight, molybdenum less than or equal to 0.1 ppm by weight and/or antimony less than or equal to 1.5 ppm by weight, optionally of zinc less than or equal to 3.0 ppm by weight.

Consequently, a subject matter of the invention is also a dental composite material and a polymerised dental composite material comprising at least one feldspar, a mixture comprising feldspar or a feldspar mixture, being obtainable by treatment of the respective feldspar with an acid, in particular an organic acid, inorganic acid or a mixture of inorganic acids selected from sulfuric acid, hydrochloric acid, nitric acid or aqua regia or a treatment with an organic acid, such as, for example, citric acid, preferably at least one feldspar, a mixture comprising feldspar or a feldspar mixture the iron content of which amounts to less than or equal to 50 ppm by weight. Preferably, the treatment is performed with a strong acid, comprising organic acids or mixtures thereof, inorganic acids or mixtures of inorganic acids, the pKa value of which amounts to less than or equal to 7.5, preferably the pKa value amounts to less than or equal to 3.5. Acid having a pKa value of less than 0 are more particularly preferred.

The following optionally additionally used dental glasses are preferably considered: aluminosilicate glasses or fluoroaluminosilicate glasses, barium aluminum silicate, strontium silicate, strontium borosilicate, lithium silicate and/or lithium aluminum silicate as well as mixtures of at least two of the aforementioned dental glasses. Amorphous spherical fillers based on oxide or mixed oxide, such as amorphous SiO₂, ZrO₂ or mixed oxides of SiO₂ and ZrO₂, may be used as metal oxide or as a mixture of amorphous metal oxides.

According to an alternative preferred embodiment, the dental composite material optionally additionally comprises at least one dental glass, in particular a radiopaque dental glass, of an average particle size d₅₀ of 0.7 to 6.5 μm, in particular i) of 0.7 to 1.0 μm, ii) of 1.2 to 1.7 μm, preferably having an average particle size of 1.35 to 1.65 μm, in particular with d₅₀ of 1.5 μm optionally plus/minus 0.15 μm, preferably plus/minus 0.10 μm, and/or with d₅₀ of 5 μm optionally plus/minus 0.5 μm, and preferably with d₉₉ less than or equal to 10 μm. An average particle size d₅₀ of about 1.5 μm optionally plus/minus 0.10 μm, in particular plus/minus 0.05 μm, preferably plus/minus 0.03 μm, and preferably with d₉₉ less than or equal to 10 μm. A particularly preferred dental glass comprises barium aluminum borosilicate glass. Moreover, a barium aluminum silicate glass having a reflective index of n=1.52 to 1.55, preferably 1.53, is particularly preferred. A particularly preferred particle size distribution may be in the range of d₁₀ with greater than or equal to 0.2 μm to d₉₉ less than or equal to 5 μm, preferably with d₁₀ greater than or equal to 0.4 μm to d₉₉ less than or equal to 2.5 μm and an average diameter d₅₀ of 1.2 to 1.7 μm.

According to a preferred embodiment, the dental composite material comprises (i) 60 to 85% by weight of at least one inorganic filler component, wherein at least one tectosilicate (without zeolitic H₂O), preferably feldspar or mixtures thereof, in particular of an average particle size d₅₀ of 1.5 to 2.5 μm is present of greater than or equal to 66 to 80% by weight, based on the composite material, in particular of greater than or equal to 66 to 75% by weight.

Furthermore, a subject matter of the invention is a dental composite material comprising (i) 60 to 85% by weight of at least one inorganic filler component comprising at least one feldspar or mixtures thereof, as well as optionally additionally at least one dental glass comprising barium aluminum borosilicate glass, barium aluminum borfluorosilicate glass, in particular silanised, preferably functionalised with methacryloxypropyl groups, as well as optionally at least one non-agglomerated amorphous metal oxide of a primary particle size of 2 to 45 nm, wherein the amorphous metal oxide comprises precipitated silicon dioxide, zirconium oxide, mixed oxides or mixtures thereof, in particular the metal oxides are silanised.

In order to achieve a high flexural strength, the dental composite material preferably comprises as inorganic filler component (i.1) 60 to 84% by weight at least one feldspar or mixtures thereof, in particular 65 to 80 71 to 76% by weight, and optionally (i.2) 0 to 20% by weight, preferably 2 to 10% by weight amorphous metal oxide, in particular 3 to 10% by weight, preferably 4 to 8% by weight, in the total composition. The ratio of feldspar to amorphous metal oxide may preferably amount to 20:1 to 5:1, preferably to 15:1 to 10:1. The inorganic filler component preferably comprises from 85 to 100% by weight, in particular 95 to 100% by weight at least one feldspar or mixtures thereof. According to a particularly preferred embodiment, the dental composite material comprises (i) 60 to 85% by weight of at least one inorganic filler component comprising (i.1) 60 to 80%, in particular 66 to 78% by weight, preferably 66 to 70% by weight or 75 to 78% by weight at least one feldspar or mixtures thereof, in particular of an average particle size d₅₀ of 1.5 to 2.5 μm, as well as optionally (i.2) 0 to 20% by weight, in particular 1 to 15% by weight at least one amorphous silanised metal oxide and/or pyrogenic silica of a primary particle size of 2 to 45 nm, based on the total composition, (ii) 10 to 40% by weight, in particular 15 to 40% by weight, preferably 20 to 40% by weight, preferably 20 to 30% by weight of a mixture of at least two different urethane(meth)acrylates, in particular of di- to decafunctional urethane(meth)acrylates, preferably from 10 to 22.5% by weight of a difunctional urethane(meth)acrylate having a bivalent alicyclic group and 5 to 17.4% by weight of a difunctional urethane(meth)acrylate having a bivalent alkylene group, and optionally 0.1 to 2% by weight of at least one hexafunctional urethane(meth)acrylate or dendritic urethane methacrylate of a mixture of urethane(meth)acrylates, and (iii) 0.01 to 5% by weight, in particular 0.5 to 3% by weight, preferably 0.8 to 2.0% by weight, of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane(meth)acrylate, in particular at least one di-, tri-, tetra- or multi-functional methacrylic ester of polyethers, preferably dimethacrylate triethylene glycol, (iv) 0.01 to 10% by weight, in particular 0.5 to 5% by weight, preferably 0.5 to 2% by weight of at least one thermal initiator, of a thermal initiator system as well as optionally of at least one stabiliser and optionally of at least one pigment, in particular of a pigment mixture comprising a pigment selected from fluorescence pigments and colour pigments, wherein the total composition of the composite material amounts to 100% by weight.

The di- to decafunctional urethane(meth)acrylates are used as monomers and do not comprise peroxy groups.

According to a particularly preferred embodiment, the dental composite material comprises (ii) 15 to 40% by weight of a mixture of at least two different urethane(meth)acrylates, preferably of three different urethane(meth)acrylates, comprising at least one difunctional urethane(meth)acrylate having a bivalent alicyclic group, and a difunctional urethane(meth)acrylate having a bivalent alkylene group, as well as optionally at least one at least tetrafunctional dendritic urethane(meth)acrylate, preferably at least one hexafunctional dendritic urethane(meth)acrylate.

Particularly preferred difunctional urethane(meth)acrylates having a bivalent alicyclic group comprise bis(4′,7′-dioxa-3′,8′-dioxo-2′-aza-decyl-9′-en)tetrahydrodicyclopentadiene, bis(4′,7′-dioxa-3′,8′-dioxo-2′-aza-9′-methyl-decyl-9′-en)tetrahydrodicyclopentadiene and/or mixtures thereof as well as optionally mixtures of the 3,8-/3,9-/4,8-/3,10-/4,10 isomers and/or of the cis isomers and trans isomers of the afore-mentioned compounds.

The difunctional urethane(meth)acrylate having a bivalent alicyclic group is preferably selected from linear or branched urethane dimethacrylates being functionalised with a bivalent alkylene group, urethane dimethacrylate-functionalised polyethers having alkylene group(s), such as bis(methacryloxy-2-ethoxycarbonylamino)alkylene, bis(methacryloxy-2-ethoxycarbonylamino)-substituted polyalkylene ethers, preferably 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane, UDMA or HEMA-TDMI. A bis(methacryloxy-2-ethoxycarbonylamino)alkylene, wherein alkylene comprises linear or branched C3 to C20, preferably C3 to C6, is preferred, such as, particularly preferably, an alkylene substituted with methyl groups, such as HEMA-TMDI. The bivalent alkylene preferably comprises 2,2,4-trimethylhexamethylene and/or 2,4,4-trimethylhexymethylene.

The at least tetrafunctional dendritic urethane methacrylate comprises tetra- to decafunctional dendritic urethane methacrylates.

It is also preferred for (ii) to comprise 20 to 40% by weight of a mixture of at least two different urethane(meth)acrylates, based on the total composition, such as at least one difunctional urethane(meth)acrylate having a bivalent alicyclic group and at least one hexafunctional dendritic urethane(meth)acrylate, and optionally at least one difunctional urethane(meth)acrylate having a bivalent alkylene group.

Preferably, the composite material comprises 5 to 25% by weight, in particular 15 to 19% by weight bis-(4′,7′-dioxa-3′,8′-dioxo-2′-aza-decyl-9′-en)tetrahydrodicyclopentadiene, Bis-(4′,7′-dioxa-3′,8′-dioxo-2′-aza-9′-methyl-decyl-9′-en)tetrahydrodicyclopentadiene and/or mixtures thereof as well as optionally mixtures of the 3,8-/3,9-/4,8-/3,10-/4,10-isomers and/or of the cis- and trans-isomers of the afore-mentioned compounds, 1 to 15% by weight, in particular 5 to 6% by weight UDMA (1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane), in particular HEMA-TMDI, and 0.1 to 5% by weight, preferably 0.2 to 2% by weight, particularly preferably 0.1 to 1% by weight of at least one tetra- to decafunctional dendritic urethane methacrylate, based on the total composition.

Preferably, the composite material comprises 15 to 40% by weight, in particular 15 to 35% by weight, of a mixture of at least three different urethane(meth)acrylates, selected from 10 to 20% by weight comprising bis-(4′,7′-dioxa-3′,8′-dioxo-2′-aza-decyl-9′-en)tetrahydrodicyclo-pentadiene, Bis-(4′,7′-dioxa-3′,8′-dioxo-2′-aza-9′-methyl-decyl-9′-en)tetrahydrodicyclo-pentadiene and/or mixtures thereof as well as optionally mixtures of the 3,8-/3,9-/4,8-/3,10-/4,10-isomers and/or of the cis- and trans-isomers of the afore-mentioned compounds, 3 to 19.9% by weight, in particular 3 to 13% by weight, of a difunctional urethane(meth)acrylate having a bivalent alkylene group, in particular UDMA or HEMA-TMDI, and 0.1 to 17% by weight, preferably 0.2 to 2% by weight, particularly preferably 0.1 to 1% by weight of at least one tetra- to decafunctional dendritic urethane methacrylate, based on the total composition.

According to a further preferred embodiment, the dental composite material comprises as component (iii) 0.01 to 5% by weight of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane acrylate and being selected from dimethacrylic esters of polyethers, tri-, tetra- or multi-functional methacrylic esters of polyethers.

Preferably, the content of components (iii) amounts to 0.15 to 5% by weight, particularly preferably 1.0 to 2% by weight, of a dimethacrylic ester of a polyether, such as preferably a dimethacrylate polyethylene glycol, dimethacrylate polypropylene glycol. Dimethacrylate triethylene glycol (TEGDMA), diethylene glycol dimethacrylate (DEGMA) and dimethacrylate tetraethylene glycol (TEDMA) are particularly preferred.

Water as stabiliser was added to the dental composite material to improve the consistency and the flow properties for the process-engineering processability. Stabilisers were added to the composite material to prevent premature polymerisation and give the material a certain shelf life. The composite material comprises as preferred stabilisers in component (iv) at least one stabiliser selected from water, at least one benzophenone derivative, preferably alkoxy-substituted benzophenone and/or phenol derivative, such as 2-hydroxy-4-methoxybenzophenone, 2,6-bis(1,1-dimethyl)-4-methylphenol, or a mixture of the three stabilisers. The stabilisers are preferably present in 0.01 to 14% by weight in the total composition, particularly preferably form 0.7 to 10% by weight, in particular from 0.5 to 2% by weight. In addition, it is preferred for the composite material to contain 0.01 to 2% by weight water as stabiliser, preferably 0.1 to 1.0% by weight water.

At least one pigment comprising at least one fluorescence pigment and optionally at least one organic colour pigment and/or at least one inorganic colour pigment, in particular non-fluorescent colour pigments, are added to the composite material for optimal adjustment of the colour and natural aesthetic of the polymerised composite material. The at least one fluorescence pigment preferably is an organic fluorescence pigment, in particular a non-polymerisable organic fluorescence pigment, where appropriate comprising aryl carboxylic acid esters, aryl carboxylic acids, coumarin, rhodamine, naphthalene imide or a derivative of the respective substance. Inorganic fluorescence pigments may comprise CaAl₄O₇:Mn²⁺, (Ba0.98Eu0.02)MgAl₁₀O₁₇, BaMgF₄:Eu²⁺, Y(1.995)Ce(0.005)SiO₅.

The composite may comprise as pigments, in particular colour pigments, organic pigments as well as inorganic pigments, in particular comprising diethyl-2,5-dihydroxy terephthalate, N,N′-Bis(3,5-xylyl)perylene-3,4:9,10-bis(dicarbimide), copper phthalocyanine, titanate pigment, in particular chromium antimony titanate (rutile structure), spinel black, in particular pigments being based on iron oxide black (Fe₃O₄), wherein iron (Fe) is partially substituted by chromium and copper or nickel and chromium or manganese, zinc iron chromium spinel, brown spinel, ((Zn,Fe)(Fe,Cr)₂O₄), cobalt zinc aluminate blue spinel and/or titanium oxide. The pigments comprising fluorescence pigments and colour pigments preferably present in 0.01 to 10% by weight in the total composition, particularly preferably from 0.01 to 5% by weight, preferably from 0.01 to 1% by weight.

Selection of pigments has to be specifically adapted to the dental composite composition in order to achieve a homogeneous colour in both the polymerisable composite and the polymerised composite. Also the production of large blocks of material requires coordination with regard to the selection and to the concentration of the pigments in order to avoid undesirable discolorations due to the dimensioning of the polymerised blocks of material.

Peroxides, hydroxyl peroxides or mixtures comprising them are suitable as initiators. Suitable thermal initiators may be used as radical initiators in the temperature range of 70 to 150° Cm preferably of 90 to 150° C. Preferred thermal initiators comprise at least one initiator selected from: tert.-butylperoxy-2-ethylhexanoate, dibenzoylperoxide, dicumylperoxide, dicumyl-hydroperoxide, azobisisobutyronitrile, benzylbarbituric acid derivative.

Another subject matter of the invention is a polymerised dental composite material obtainable by polymerisation of the composite material according to the invention, in particular by polymerisation of the composite material at a pressure of 500 to 300 MPa (=[N/mm²]), in particular at 50 to 300 MPa, preferably at 100 to 300 MPa, particularly preferably at 120 to 200 MPa, preferably at 120 to 170 MPa, and at elevated temperature, preferably at 90 to 150° C. Polymerisation is preferably carried out in a casting mould, preferably having a geometric shape. The polymerisation under elevated pressure minimises or avoids air bubble formation in the polymerised composite material.

The shrinkage of the polymerisable composite material preferably amounts to less than or equal to 2.0%, in particular less than 1.5%, particularly preferably less than or equal to 1.4% ((Bonded-Disc method—Dental Materials, Watts et al, (2004) 20, 88-95; 23° C., Translux Energy, 60 s exposure). The polymerised composite material preferably has no blowholes or cracks of a size of greater than or equal to 200 nm, in particular a block of material has no blowholes or cracks. The polymerised composite material has a density of greater than or equal to 2.0 g/cm³, in particular a density of greater than or equal to 2.1 g/cm³.

Surprisingly, the polymerised dental composite material, in particular being obtainable by thermal polymerisation of the composite material, has a synergistic combination of a high flexural strength and an elastic modulus in the range of the hard tooth tissue. The flexural strength and the elastic modulus may be measured by keeping thermally polymerised test specimens for 7 days under dry conditions at ambient room temperature (23±2° C.) or by storing test specimens in 37° C. deionised water for 7 days, followed by 5000 thermal cycles (5° C. to 55° C., retention time 30 seconds) by means of a thermocyclic device (HA-K178, Tokyo Giken Inc., Tokyo, Japan) and subsequently measuring the flexural strength and the e-modulus. The flexural strength and the elastic modulus were prepared and measured (dry as well as after 7 days of storage in water) analogous to Dent. Materials J 2014; 33(4/5), 705 to 710, i.e. according to EN ISO 6872:2008 or with additional water storage.

The ISO 6872 standard was developed for testing ceramic materials being available as CAD/CAM blocks. Since the composite materials are also produced and machined in the same dimensioning, a comparable analogous test with water storage should be carried out. The production of test specimens according to the composite standard (ISO4049) cannot be carried out from one block due to the dimensions of the test specimens.

While the flexural strength of a dental composite is not limited to high values, (>100 MPa), a balanced/optimal elasticity is advantageous for the application. The elastic modulus should ideally correspond to that of the dentin of the hard tooth tissue so that failure in the intended application is avoided as far as possible. Materials that are too brittle (having a high e-modulus) tend to chipping or fracture. Materials that are too elastic (low e-modulus) deform under chewing load and the cementation detaches (debonding).

The material properties (flexural strength and e-modulus) of human hard tooth tissue are known from literature (Dwayne D. Arola et al. Biomaterials 27(2006) 2131-2140) as a function of orientation (anisotropic material properties due to crystal orientation). There, the elastic modulus of human hard tooth structure is between 15 to 19 GPa, depending on the orientation. The aim was therefore to provide a composite having an e-modulus (elastic modulus) being in the range of human hard tooth tissue, thus preferably in the range of 15 to 20 GPa, to mimic toothlike properties.

Thus, another subject matter of the invention is a polymerised dental composite material, in particular thermally polymerised composite material, preferably for 10 minutes to 10 hours at 80 to 150° C., in particular at 90 to 150° C., polymerised composite material having a flexural strength of greater than or equal to 240 MPa to optionally 330 MPa, in particular 280 to 330 MPa (7 days, 23±2° C., dry storage) and an elastic modulus greater than or equal to 16 to 21 GPa, in particular 18 to 21 GPa (7 days, 23±2° C., dry storage) according to EN ISO 6872:2008, wherein the polymerised composite material optionally additionally has a flexural strength of greater than or equal to 260 MPa to 330 MPa, in particular of 270 to 330 MPa (7 days in H₂O deionised at 37° C.) and an elastic modulus of greater than or equal to 16 to 22 GPa, in particular of 18 to 22 GPa (7 days in H₂O deionised at 37° C.) according to EN ISO 6872:2008. Particularly preferably, the polymerised dental composite material has a flexural strength of greater than or equal to 240 Mpa to 300 MPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles, in particular ca. 5000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds)) and an elastic modulus greater than or equal to 15 to 22 GPa, in particular 16 to 20 GPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles, in particular 5000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds, to 60 seconds where applicable)) according to EN ISO 6872:2008.

The method of the execution examples is analogous to the method being indicated in Dent. Mater. J. 2014; 33(5) 705-710. The publication also compares in Table 3 further results of the three-point bending flexural test according to this method for CAD/CAM blocks of different dental materials. The dental materials measured in the afore-mentioned literature have flexural strengths after dry storage of 170 Mpa and an e-modulus of 9.6 or 14.5 GPa, as well as a flexural strength of 117.6 MPa or 120.1 MPa and an e-modulus of 7.2 or 12.2 GPa after thermocycling (thermos cycles). Even dental materials having a flexural strength of 242 or 204 MPa and an e-modulus of 10.0 or 14.7 GPa after dry storage only have flexural strength of 194.3 or 165.1 MPa at an e-modulus of 8.7 GPa or 13.2 GPa. It is therefore clear that setting an e-modulus analogous to that of the hard tooth tissue in the range of 15 to 20 GPa at both dry storage and also a storage at 37° C. plus thermocycling had not been possible so far.

TABLE 1 Flexural strength in MPa and e-modulus in GPa of Table 3 in Dent. Mater. J. 2014; 33(5) 705-710 Vita- Block Cera- Gradia Lava Vita blocs Condition HC smart Block Ultimate Enamic Mark II flexural dry 170.5 242.0 204.0 170.5 140.7 126.6 strength water 121.5 197.3 188.4 141.9 133.0 121.1 [MPa] water/TC 117.6 194.3 165.1 120.1 134.6 129.0 e-modulus dry 9.6 10.0 14.7 14.5 28.5 51.5 [GPa] water 7.8 9.0 13.5 12.8 28.3 52.8 water/TC 7.2 8.7 13.2 12.2 28.6 54.9

According to a particularly preferred embodiment, a subject matter of the invention is polymerised dental composite material comprising 60 to 85% by weight of at least one inorganic filler component comprising at least one feldspar, in particular of an average particle size d₅₀ of 2.0 μm optionally plus/minus 0.5 μm, as well as optionally at least one amorphous silanised metal oxide in particular precipitated silicon dioxide and/or pyrogenic silica, in particular of a primary particle size of 2 to 45 nm, 10 to 40% by weight of at least one polymer being based on at least one monomer, preferably being based on a mixture of the following monomers, comprising at least one bis-urethane derivative of tetrahydrodicyclopentadiene, in particular a difunctional urethane(meth)acrylate of tetrahydrodicyclopentadiene and at least one diurethane(meth)acrylate having a bivalent alkylene group, at least one tetra- to decafunctional dendritic urethane methacrylate, and at least one di-, tri-, tetra- or multi-functional methacrylic ester of polyethers, preferably dimethacrylate triethylene glycol, and 0.01 to 10% by weight of at least one pigment, in particular of at least one fluorescence pigment and of at least one organic colour pigment and/or of at least one inorganic colour pigment, wherein the colour pigments preferably do bot fluoresce, wherein the total composition of the composite material amounts to 100% by weight.

The polymerised dental composite material may preferably be present in the form of a block of material, in particular as three-dimensional block of material in the form of a geometric moulded body, in particular in the form of a milling blank with an adapter for fastening in an automated device to remove material, particularly preferably in the form of a cylinder, of a cuboid, preferably in the form of a cube. In addition, it is preferred for the edges and/or vertices of the moulded body to be rounded. The dimensions of the cylinder preferably have a height of greater than or equal to 10 mm to less than or equal to 15 mm and a radius of greater than or equal to 3 to less than or equal to 7 mm, alternatively a height of greater than or equal to 10 mm to less than or equal to 20 mm and a radius of greater than or equal to 5 to less than or equal to 7 mm. The dimensions of the cuboid for a, b, and c preferably amounts to greater than or equal to 4 mm, in particular greater than or equal to 10 mm and a less than or equal to 20 mm, in particular less than or equal to 18 mm, b less than or equal to 14 mm and c less than or equal to 20 mm, in particular less than or equal to 18 mm. Preferably, a three-dimensional block of material as at least an edge length of at least 10 mm each, preferably of 14 mm. Blocks of material being us as milling blanks preferably have the shape of cuboids, wherein the cuboids preferably have a volume of 12 mm×14 mm×17 or 18 mm, alternatively of 14×14 mm, or 15×15 mm as well as a height of 17 to 18 mm. One to all edges and vertices may be straight or rounded.

Furthermore, a subject matter of the invention is the use of a dental composite material for the production of dental prosthetic restorations, in particular for the production of indirect dentures, in a material-removing process, in particular in a process in which the polymerised composite material is removed by means of milling, cutting, polishing, breaking, chipping and/or drilling, particularly preferably in a process in which the composite material is removed by means of laser energy. A particularly preferred use for the material is the use in a method for the production of dental prosthetic restorations in a material-removing process, in which the material is removed by means of laser energy. The particle size as well as preferably the particle size distribution was specially adapted to a method in which the polymerised composite material is removed by means of laser energy and the prosthetic restorations may be produced.

or for the production of direct adhesive dental restorations. A particular advantage of the dental material according to the invention is that it allows the possibility of a significant process simplification in the production of indirect dentures by the dentist or dental technician carrying out at least one intraoral scan in the patient's mouth and may subsequently use the digital dental information obtained in this way to directly fabricate a prosthetic dental restoration, such as a crown or an inlay, taking into account other device parameters, etc. The dental prosthetic restoration produced may then be inserted at the patient, fixed and, if necessary, slightly reprocessed. For example, an intraoral scan is taken before grinding a tooth to produce a tooth stump for a crown and another intraoral scan of the tooth stump.

Furthermore, the polymerised composite material may be used for the production of dental prosthetic restorations comprising crowns, inlay, onlays, superstructures, artificial teeth, dental bridges, dental bars, spacers, abutments or veneers. The polymerised composite material may additionally be used as composite material for the production of direct adhesive dental restorations.

The following are also preferably considered to be urethane(meth)acrylates according to the invention: (ii) at least one urethane(meth)acrylate, in particular a urethane dimethacrylate, preferably a bis(methacryloxy-2-ethoxycabonylamino)alkylene, diurethane acrylate oligomers, alkyl-functional urethane dimethacrylate oligomers, aromatic-functionalised urethane dimethacrylate oligomers, aliphatic unsaturated urethane acrylates, bis(methacryloxy-2-ethoxycarbonylamino)-substituted polyethers, aromatic urethane diacrylate oligomers, aliphatic urethane diacrylate oligomers, aliphatic urethane diacrylates, hexafunctional aliphatic urethane resins, aliphatic urethane triacrylates, aliphatic urethane acrylate oligomers, unsaturated aliphatic urethane acrylates. Difunctional and multi-function urethane(meth)acrylates are preferred, such as, in particular, urethane di(meth)acrylate, the at least one (iii) urethane dimethacrylate is particularly preferably selected from linear or branched alkyl-functionalised urethane dimethacrylates, urethane dimethacrylate-functionalised polyethers, in particular bis(methacryloxy-2-ethoxycarbonylamino)alkylene, bis(methacryloxy-2-ethoxycarbonylamino)-substituted polyethers, preferably 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane. Suitable urethane(meth)acrylates are available under the following brand names: Ebecryl 230 (aliphatic urethane diacrylate), Actilane 9290, Craynor 9200 (Diurethane acrylate oligomer), Ebecryl 210 (aromatic urethane diacrylate oligomers), Ebecryl 270 (aliphatic urethane diacrylate oligomers), Actilane 165, Actilane 250, Genomer 1122 (monofunctional urethane acrylate), Photomer 6210 (cas no. 52404-33-8, aliphatic urethane diacrylate), Photomer 6623 (hexafunctional aliphatic urethane resin), Photomer 6891 (aliphatic urethane triacrylate), UDMA, Roskydal LS 2258 (aliphatic urethane acrylate oligomer), Roskydal XP 2513 (unsaturated aliphatic urethane acrylate). The urethane (meth)acrylates may preferably be selected from the afore-mentioned urethane (meth)acrylates or from a mixture of at least two different, preferably at least three different, afore-mentioned urethane(meth)acrylates.

The at least one di-, tri-, tetra- or multi-functional monomer not being urethane (meth)acrylate is preferably selected from at least one of the following monomers, in particular a mixture of monomers comprising 1,4-butandiol dimethacrylate (1,4-BDMA) or pentaerythritol tetraacrylate, bis-GMA monomer (bisphenol-A-glycidyl methacrylate), triethylene glycol dimethacrylate (TEGDMA) and diethylene glycol dimethacrylate (DEGMA), tetraethylene glycol di(meth)acrylate, decanediol di(meth)acrylate, dodecandiol di(meth)acrylate, hexyldexandiol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate as well as butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated/propoxylated bisphenol-A-di(meth)acrylate, of a mixture comprising at least one of these (meth)acrylates and/or copolymers comprising one or at least two of the aforementioned monomers.

Typical difunctional monomers, also referred to as crosslinker and/or multi-crosslinker, include tri- or tetraethylene glycol di(meth)acrylate, BDMA, 1,4-butandiol dimethacrylate (1,4-BDMA), bis-GMA monomer (bisphenol-A-glycidylmethacrylate, an addition product of methacrylic acid and bisphenol-A diglycidylether), diethylene glycol di(meth)acrylate, bisphenol-A di(meth)acrylate, decanediol di(meth)acrylate, dodecandiol di(meth)acrylate, hexyldexandiol di(meth)acrylate as well as butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated/propoxylated bisphenol-A-di(meth)acrylate. The following difunctional monomers may also be added as diluting agent (low viscosity acrylates). Tri- and tetrafunctional monomers and/or multi-crosslinkers comprise trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)-isocyanurate triacrylate, pentaerythritol tetraacrylate.

At least one of the following monomers may be present in the composite material in addition to the di-, tri- or multi-functional monomer or monomers, comprising at least one monomer, in particular a mixture of monomers of methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, n-hexyl methacrylate, 2-phenoxyethylmethacrylate, isobornylmethacrylate, isodecylmethacrylate, polypropylene glycol monomethacrylate, tetrahydrofurylmethacrylate, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, n-hexylacrylate, 2-phenoxyethylacrylate, isobornylacrylate, isodecylacrylate, polypropylene glycol monoacrylate, tetrahydrofurylacrylate, hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, benzyl-, furfuryl- or phenyl(meth)acrylate, a mixture containing at least one of these (meth)acrylates and/or copolymers comprising one or at least two of the aforementioned monomers.

Furthermore, a subject matter of the invention is a composite material comprising, preferably additionally, at least one or more substance(s) from the groups consisting of fillers, pigments, stabilisers, regulators, antimicrobial additives, UV-absorbing agents, thixotroping agents, catalysts and crosslinkers. Rather small amounts of said additives—as also of pigments, stabilisers and regulators—are used, e.g. a total of 0.01 to 3.0, in particular 0.01 to 1.0% by weight, based on the total mass of the material. Suitable stabilizers include e.g. hydroquinone monomethylether or 2,6-di-tert.-butyl-4-methylphenol (BHT).

The following initiators and/or initiator systems for auto- or cold-polymerisation comprise a) at least one initiator, in particular at least one peroxide and/or azo compound, in particular LPO: dilauroylperoxide, BPO: dibenzoylperoxide, t-BPEH: tert.-butyl-peroxy-2-ethylhexanoate, AIBN: 2,2′-azobis-(isobutyronitrile), DTBP: di-tert-butylperoxide, and, optionally, b) at least one activator, in particular at least one aromatic amine, such as N, N-dimethyl-p-toluidine, N,N dihydroxyethyl-p-toluidine and/or p-dimethylaminobenzoic acid diethylester, or c) at least one initiator system selected from redox systems, in particular a combination selected from dibenzoylperoxide, dilauroylperoxide, and camphorquinone with amines selected from N,N dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine, and p-dimethylamino-benzoic acid diethylester. The initiator may alternatively be a redox system comprising a peroxide, and a reduction agent selected from ascorbic acid, ascorbic acid derivative, barbituric acid or a barbituric acid derivative, sulfinic acid, sulfinic acid derivative, particularly preferred is a redox system comprising (i) barbituric acid or thiobarbituric acid or a barbituric acid derivative or thiobarbituric acid derivative, and (ii) at least one copper salt or copper complex, and (iii) at least one compound having an ionic halogen atom, particularly preferred is a redox system comprising 1-benzyl-5-phenylbarbituric acid, copper acetylacetonate, and benzyldibutylammonium chloride. Particularly preferably, the polymerisation in the two-component prosthetic base material is started by a barbituric acid derivative.

In general, Initiators for the polymerisation reaction of cold- or auto-polymerising starting mixtures are considered to be those with which radical polymerisation reactions may be startet. Preferred initiators are peroxides as well as azo compounds, such as, for example, the following: LPO: dilauroylperoxide, BPO: dibenzoylperoxide, t-BPEH: tert.-butylperoxi-2-ethylhexanoate, AIBN: 2,2′-azobis-(isobutyronitrile), DTBP: di-tert.-butylperoxide.

In order to accelerate the initiation of radical polymerisation by peroxides, suitable activators, e.g. aromatic amines, may be added. Examples of suitable amines are N,N-dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine and p-dibenzylaminobenzoic acid diethylester. In this context, the amines regularly function as co-initiators and are usually present in an amount of up to 0.5% by weight.

The below execution examples shall clarify the invention without limiting it to these examples.

EXECUTION EXAMPLES

Three-Point Bending Flexural Test

Flexural properties were determined using a three-point bending flexural test according to ISO 6872:2008 (ISO 6872:2008. Dentistry—Ceramic materials, 3rd ed, International Organization for Standardization, Geneva, 2008). The rod-shaped specimens, 4.0 mm wide, 14.0 mm long and 1.2 mm thick, were produced with a low-speed diamond saw (Isomet, Buehler, Lake Bluff, Ill., USA). All specimens were wet ground and polished with a #600 and #1000 diamond wheel (Maruto, Tokyo, Japan) and #1000 diamond blades (Maruto) mounted on a metallographic lapping machine (Dia-Lap, ML-150P, Maruto) to achieve the required dimensions of 4.0±0.2×14.0±0.2×1.2±0.2 mm. In order to minimize edge breaks in the rod-shaped specimens during the bending test, an edge chamfer, 0.15 mm wide, was incorporated using the lapping machine with a #1000 diamond blade. After polishing, all specimens were stored in a silica gel desiccator for 7 days prior to the bending flexural test. Three groups of ten specimens each were randomly produced from each CAD/CAM block. Specimens of the first group were stored under dry conditions at ambient room temperature (23±2° C.) for 7 days. The second group was stored in 37° C. deionized water for 7 days, while the third group was stored in 37° C. deionized water for 7 days followed by 5000 thermal cycles (thermal cycles=TZ; 5° C. to 55° C., retention time 30 s) using a thermocyclic device (HA-K178, Tokyo Giken Inc., Tokyo, Japan). The width and thickness of each specimen were measured using a digital micrometer (MDC-25M, Mitsutoyo Co., Tokyo, Japan; minimum value: 0.001 mm). A three-point bending flexural test with a support span of 12.0 mm and a traverse speed of 1.0 mm/min was performed at ambient room temperature (23±2° C.) by means of a universal testing machine (AG-X, Shimadzu Corp., Kyoto, Japan). The flexural strength and the flexural modulus were calculated by use of software (TRAPEZIUM X, Shimadzu Corp., Kyoto, Japan). The flexural modulus (E) was calculated according to the following formula: E=FL ³/4bh ³ d wherein F represents the load at an appropriate point in the linear part of the spring characteristics, L the support span (12.00 mm), b the width of the specimen, h the thickness of the specimen and d the bending at a load F. The flexural strength (a) was calculated with the following formula: σ=3F ₁ L/2bh ² wherein F₁ represents the maximal load during the bending flexural test.

The hardness test was carried out using a Zwick universal device: The measured values of the specimens according to the invention are in the range of 800 to 850.

In the following, comparative examples of light-curing products Venus Diamond (VD) and Venus Pearl (VP) have been measured according to ISO 4049 and ISO 6872 (The exposure was carried out point by point according to the method described in EN ISO 4049:2009 7.11 using a Translux 2Wave (1200 mW/cm²) by means of an exposure time of respectively 20 seconds per exposure point.) and compared with Example 1 according to the invention.

TABLE 2 Comparison Ex. 1 with Venus products Comparative examples Venus Venus Diamond Pearl Example 1 (VD) (VP) Flexural strength [MPa] 291 MPa 182 MPa 195 MPa according to EN ISO 6872 Elastic modulus [GPa] 19.3 GPa 15.6 GPa 15.8 GPa according to EN ISO 6872 Flexural strength [MPa] 174 MPa 149 MPa according to EN ISO 4049 (24 h/water) Elastic modulus [GPa] 12.0 GPa 11.4 GPa according to EN ISO 4049 (24 h/water)

TABLE 3 Composition according to the invention Examples 1 to 3: Examole 1 2.0 μm feldspar d₅₀ % by weight g filler feldspar 69.21% 69.21 metal oxide amorphous SiO₂ 5.96% 5.96 urethane(meth)- bis(4′,7′-dioxa-3′,8′-dioxo-2′- 15.68% 15.686 acrylates aza-decyl-9′-en)tetrahydro- dicyclopentadiene urethane methacrylate 0.75% 0.75 dendrimer, hexafunctional 7,7,9-trimethyl-4,13-dioxo- 5.59% 5.59 3,14-dioxa-5,12-diaza- hexadecane-1,16- diylbismethacrylate di- to multi- 1,2-bis(2-(methacryloyloxy)- 1.35% 1.35 funktional ethoxy)ethane monomers initiator system tert.-butylperoxy-2- 0.37% 0.37 ethylhexanoate stabiliser 2,6-bis(1,1-dimethylethyl)-4- 0.04% 0.04 methylphenol 2-hydroxy-4-methoxy- 0.30% 0.3 benzophenone water 0.60% 0.6 pigments and diethyl-2,5-dihydroxy- 0.15% 0.15 others terephthalate, colour pigments

Polymerisation of the dental composites according to the invention was performed for ca. 3 h at 95° C. After polymerisation, the flexural strength amounts to 291 MPa and the elastic modulus to 19.33 MPa.

TABLE 4 Flexural strengths (according to EN ISO 6872) after 7 days (RT) 24 h/ after thermal dry water 7 day/water cycles*/water Example 1 290 MPa 284 MPa 251 MPa *5000 7 days 37° C. H₂O 5000 thermal cycles

TABLE 5 E-modulus (elastic modulus) after 7 days (RT) 24 h/ after thermal dry water 7 days/water cycles*/water Example 1 19.5 GPa 20.1 GPa 17.3 GPa *5000 7 days 37° C. H₂O 5000 thermal cycles 

The invention claimed is:
 1. A polymerisable dental composite material, comprising (i) 60 to 85% by weight of an inorganic filler component comprising at least one tectosilicate comprising 60 to 80% by weight, based on a total weight of the composite material, of at least feldspar or a mixture thereof, (ii) 10 to 40% by weight of a mixture of at least two different urethane (meth)acrylates, (iii) 0.01 to 5% by weight of at least one di-, tri-, tetra- or multi-functional monomer not being a urethane (meth)acrylate, (iv) 0.01 to 10% by weight of at least one initiator, of an initiator system, as well as optionally of at least one stabiliser and optionally of at least one pigment, wherein the total composition of the composite material amounts to 100% by weight.
 2. The dental composite material according to claim 1, wherein the tectosilicate has an average particle size d₅₀ of 0.7 to 3.0 μm.
 3. The dental composite material according to claim 1, wherein the inorganic filler component comprises at least one tectosilicate, as well as optionally at least one dental glass and/or at least one amorphous metal oxide.
 4. The dental composite material according to claim 1, wherein (ii) comprises a mixture of at least two different urethane (meth)acrylates, wherein the mixture comprises at least one difunctional urethane(meth)acrylate having a bivalent alicyclic group and a difunctional urethane (meth)acrylate having a bivalent alkylene group, and optionally at least one at least tetrafunctional dendritic urethane (meth)acrylate.
 5. The dental composite material according to claim 1, wherein (ii) is selected from di-methacrylic esters of polyethers, tri-, tetra- or multi-functional methacrylic esters of polyethers.
 6. The dental composite material according to claim 1, wherein the at least one stabiliser comprises water, at least one benzophenone derivative and/or at least one phenol derivative.
 7. A polymerised dental composite material obtainable by polymerisation of the composite material according to claim
 1. 8. The polymerised dental composite material according to claim 7 having a flexural strength of greater than or equal to 240 MPa to optionally 330 MPa (7 days, 23±2° C., dry storage), and an elastic modulus greater than or equal to 16 to 21 GPa, (7 days, 23±2° C., dry storage) according to EN ISO 6872:2008.
 9. The polymerised dental composite material according to claim 7 having a flexural strength of greater than or equal to 260 MPa to 330 MPa (7 days of storage in H₂O deionised at 37° C.), and an elastic modulus greater than or equal to 16 to 22 GPa (7 days of storage in H₂O deionised at 37° C.) according to EN ISO 6872:2008.
 10. The polymerised dental composite material according to claim 7 having a flexural strength of greater than or equal to 240 MPa to 300 MPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds)), and an elastic modulus greater than or equal to 15 to 22 GPa (7 days of storage in H₂O deionised at 37° C., followed by greater than or equal to 1000 cycles (5° C. to 55° C., retention time greater than or equal to 30 seconds)) according to EN ISO 6872:2008.
 11. A polymerised dental composite material comprising 60 to 85% by weight of at least one inorganic filler compound comprising 60 to 80% by weight of at least one feldspar, as well as optionally at least one dental glass, and/or at least one amorphous silanised metal oxide of a primary particle size of 2 to 45 nm, 10 to 40% by weight of at least one polymer being based on at least one monomer comprising at least one bis-urethane derivative of tetrahydrodicyclopentadiene, at least one di-urethane (meth)acrylate having a bivalent alkylene group, at least one tetra- to decafunctional dendritic urethane methacrylate, and at least one di-, tri-, tetra- or multi-functional methacrylic ester of polyethers, and 0.01 to 10% by weight of at least one pigment, wherein the total composition of the composite material amounts to 100% by weight.
 12. The polymerised dental composite material according to claim 7, wherein the polymerized dental composite material is present in the form of a block of material.
 13. Method of using a dental composite material according to claim 1 for the production of dental prosthetic restorations in a material-removing process, or for the production of direct adhesive dental restorations.
 14. Method according to claim 13 for the production of dental prosthetic restorations comprising crowns, inlay, onlays, superstructures, artificial teeth, dental bridges, dental bars, spacers, abutments or veneers.
 15. Dental composite material according to claim 1, wherein in that the tectosilicate has an average particle size i) d₅₀ of 1.3 to 2.5 μm, optionally d₅₀ of 2.0 μm with plus/minus 0.25 ii) d₅₀ of 1.5 μm with plus minus 0.25 μm, and/or iii) d₅₀ of 0.85 μm with plus/minus 0.15 μm.
 16. The polymerized dental composite material according to claim 11, wherein the polymerized dental composite material is present in the form of a block of material.
 17. Method of using a dental composite material according to claim 7 for the production of dental prosthetic restorations in a material-removing process, or for the production of direct adhesive dental restorations.
 18. Method of using a dental composite material according to claim 11 for the production of dental prosthetic restorations in a material-removing process, or for the production of direct adhesive dental restorations. 